Last updated on:December 13th, 2021
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Measles is a highly contagious communicable disease caused by an RNA virus—a member of the Morbillivirus genus in the Paramyxoviridae family. Infection is characterized by fever, malaise, cough, coryza, and conjunctivitis, followed by an exanthem. The clinical spectrum ranges from “classic” measles infections to severe disease with respiratory and neurological complications.
Measles occurs worldwide, but is predominantly seen areas with low vaccination rates—particularly low-resource settings. In high-resource settings, outbreaks occur in areas where vaccination uptake has declined. Importantly, there is no seasonal variation—i.e., measles outbreaks can occur at any point of the year. The attack rate in a susceptible individual exposed to the virus is 90%. No animal reservoirs maintain virus transmission, so measles has been targeted for eradication. However, elimination has been achieved in only a few areas of the planet.
Measles is transmitted through respiratory droplets, airborne spread, and close person-to-person contact. Infectious droplets can remain airborne for up to two hours. The virus first spreads to local lymphoid tissue. It is then disseminated throughout the bloodstream through infected lymphocytes, infecting tissues in almost all organ systems.
Measles is a vaccine-preventable disease. Measles vaccines are attenuated viral vaccines which can be combined with other vaccines—e.g., with those for rubella (MR), mumps (MMR), or varicella (MMR-V). The world health organization (WHO) recommends two doses as the standard for all national immunization programs for children. In countries with low-level measles virus transmission, the first routine dose is administered at 12 months of age or older; and the second dose can be administered at 15–18 months of age or at school entry. In countries with ongoing transmission in which the risk of measles mortality remains high, the first routine dose should be given earlier—at 9 months of age. MMR vaccines should not be administered to pregnant women and severely immunosuppressed persons.